Temperature-Dependent Fluorescence Properties and Diode-Pumped Deep Red Laser Performance of Pr:LiGdF4 Crystal

We demonstrate the temperature-dependent fluorescence properties of Pr：LiGdF4 crystal tor the first time, to the best of our knowledge, and its blue diode pumped cw red laser at 720 nm at room temperature. The fluorescence lifetime and polarized emission cross sections in the visible range are measured and calculated in a temperature range from 77K to 300 K, and the variations of the fluorescence lifetime and spectra are discovered. The reasons for these changes are explained accordingly. The output wavelength of the 720nm laser is first reported on the laser performance by using a fiber-coupled laser diode at the wavelength of 442nm as the pump source, and the maximum cw output power is about 303roW.

Application of Laser Induced Breakdown Spectroscopy in Early Detection of Red Palm Weevil:(Rhynchophorus ferrugineus)Infestation in Date Palm

The Kingdom of Saudi Arabia is one of the leading date producing countries. Unfortunately, this important fruit crop is under great threat from the red palm weevil （RPW） （Rhynchophorus ferrugineus）, which is a highly invasive pest. Several techniques, including visual inspection, acoustic sensors, sniffer dogs, and pheromone traps have been tried to detect the early stages of a RPW infestation; however, each method has suffered certain logistical and implementation issues. We have applied laser induced breakdown spectroscopy （LIBS） for the early detection of RPW infestation. Through the analysis of the observed LIBS spectra of different infested and healthy samples, we have found presence of Ca, Mg, Na, C, K elements and OH, CN molecules. The spectra also reveal that with the population growth of the pest, the intensity of Mg and Ca atomic lines in LIBS spectra increases rapidly. Similar behavior is observed in the molecular lines of LIBS spectra. The obtained results indicate that the LIBS technique can be used for the early detection of RPW infestation without damaging the date palms.

Red Shift and Broadening of Backward Harmonic Radiation from Electron Oscillations Driven by Femtosecond Laser Pulse

The characteristics of backward harmonic radiation due to electron oscillations driven by a linearly polarized fs laser pulse are analysed considering a single electron model. The spectral distributions of the electron＇s backward harmonic radiation are investigated in detail for different parameters of the driver laser pulse. Higher order harmonic radiations are possible for a sufficiently intense driving laser pulse. We have shown that for a realistic pulsed photon beam, the spectrum of the radiation is red shifted as well as broadened because of changes in the longitudinal velocity of the electrons during the laser pulse. These effects are more pronounced at higher laser intensities giving rise to higher order harmonics that eventually leads to a continuous spectrum. Numerical simulations have further shown that by increasing the laser pulse width the broadening of the high harmonic radiations can be controlled.

Red-shift law of intense laser-induced electro-absorption in solids

A theoretical study on the red-shift of laser-induced electro-absorption is presented. It is found that laser-induced red-shift scales with the cube root of the pump laser intensity in the optical tunneling regime and has an obvious deviation from this scale in the multi-photon regime. Our results show that in the optical tunneling regime, the laser-induced red shift has the same law as that in the direct current （DC） approximation. Though the scales are the same in the optical tunneling regime, the physical pictures in the two cases are quite different. The electro-absorption in the DC case is a tunneling-assisted transition process, while the laser-induced electro-absorption is a mixed multi-photon process.

High-Power Continuous-Wave Diode-End-Pumped Intracavity Frequency Doubled Nd：YVO4 Laser at 671 nm with a Compact Three-Element Cavity

We report a high-power high-efficient continuous-wave （cw） diode-end-pumped Nd：YVO4 1342-nm laser with a short plane-parallel cavity and an efficient cw intracavity frequency-doubled red laser at 671 nm with a compact three-element cavity. At incident pump power of 20.6 W, a maximum output power of 7 W at 1342 nm is obtained with a slope effciency of 37.3%. By inserting a type-Ⅰ critical phase-matched LBO crystal as intracavity frequencydoubler, a cw red output as much as 2.85-W is achieved with an incident pump power of 16.9 W, inducing an optical-to-optical conversion efficiency of 16.9%. To the best of our knowledge, this is the highest output of diodepumped solid-state Nd：YVO4 red laser. During half an hour, the red output is very stable, and the instability of output power is less than 1%.

经尿道红激光剜除术治疗巨大前列腺增生的临床疗效分析

目的探讨经尿道红激光剜除术治疗巨大前列腺增生的疗效。方法160例巨大前列腺增生(体积>80 ml)患者,采用随机数字表法分为对照组和研究组,每组80例。对照组患者采用经尿道前列腺电切术治疗,研究组患者开展经尿道红激光剜除术治疗。比较两组患者手术指标、症状评分、最大尿流率、残余尿量、术后并发症发生情况。结果研究组患者手术时间(58.32±6.02)min、住院时间(6.23±1.02)d短于对照组的(70.57±7.21)min、(7.88±1.06)d,术中出血量(166.11±8.22)ml少于对照组的(319.21±7.21)ml(P<0.05)。术前、术后3个月,两组患者国际前列腺症状评分表(IPSS)评分、最大尿流率、残余尿量比较差异不明显(P>0.05);术后3个月,两组患者IPSS评分、最大尿流率、残余尿量均较本组治疗前改善(P<0.05)。研究组患者术后并发症发生率为1.25%,低于对照组的11.25%(P<0.05)。结论采用经尿道红激光剜除术对巨大前列腺增生患者进行治疗,相比传统的经尿道前列腺电切术疗效更好,创伤性更小,安全系数更高,术后恢复更快,并发症更少。

大功率半导体激光器端面特性改善的研究

针对大电流下前腔面不稳定导致出现灾变性光学损伤(COMD)的问题,提出一种双区电极的半导体激光器,并对该结构激光器的COMD阈值、峰值功率、阈值电流、光谱稳定性及翘曲效应进行研究。在相同工艺条件下测试了单一电极结构和双区电极结构半导体激光器的COMD阈值、峰值功率、阈值电流、波长红移速度等参数。结果表明:在同等工艺条件下,主增益区阈值电流为80 mA,阈值电流降低20%,在窗口区15 mA电流的驱动下,双区电极的半导体激光器对比单电极半导体激光器COMD阈值能够提高13%、峰值功率能够提高12%,同时减少了波长红移并改善了翘曲效应。

高功率1550 nm氧化限制型VCSEL设计与仿真

1550 nm垂直腔面发射激光器具有良好的人眼安全性和透射性,但实现其高效率和高功率输出一直是难以解决的问题。以1550 nm氧化限制型垂直腔面发射激光器为研究目标,对不同结构、不同氧化孔径与输出特性关系进行仿真分析。随着氧化孔径增加,垂直腔面发射激光器芯片的激射波长发生红移现象,但氧化孔径从14μm继续增大时,激射波长几乎不红移。对两种不同氧化限制结构的芯片进行仿真,输出功率和转换效率对比结果表明单氧化层结构性能更好。在设计多结垂直腔面发射激光器时考虑有源区之间是否增加氧化层,最终发现两种氧化限制结构均在9μm孔径时具有较高的输出功率,单层结构100 mA时的输出功率约为177.55 mW,同时斜率效率也高达1.79 W/A,最大功率转换效率为10μm孔径时的37.7%,多层结构斜率效率更高达2.36 W/A。氧化限制型结构在多结垂直腔面发射激光器基础上进一步提升功率、效率等参数,可为高功率1550 nm垂直腔面发射激光器的输出特性优化提供参考。

激光熔融系统送粉喷嘴高温摩擦化学磨损行为及机制

激光熔融系统在使用过程中,高温环境下待加工粉末流会导致送粉喷嘴内壁严重磨损,而因设备结构复杂、影响因素众多等,送粉喷嘴的损伤机制尚不清晰。通过喷嘴损伤案例分析和摩擦磨损模拟实验,结合扫描电子显微镜(SEM)和能谱仪(EDS)等表征手段,对激光熔融系统送粉喷嘴的磨损规律以及高温损伤机制进行研究。结果表明:送粉喷嘴出口处更靠近高温源,因而磨损较其他区域更为严重,其磨损形式由机械应力导致的轻微疲劳磨损和磨粒磨损转变为由摩擦化学主导的严重摩擦化学磨损;在温度-应力多物理场耦合作用下喷嘴材料发生的氧化反应导致界面疏松容易被机械去除;此外摩擦界面生成的脆性钛铜金属间化合物也是导致喷嘴出口处容易被磨损的原因之一。研究结果为高温下送粉喷嘴的设计和应用提供了理论支持。

Laser treatment in 341 patients with exudative agerelated macular degeneration

AIM:To document the prognosis of laser treatment in patients with exudative age-related macular degeneration(AMD).· METHODS:Efficacy of the intervention was evaluated using a before-after method.· RESULTS:A total of 392 eyes of 341 patients with exudative AMD were examined.77.6% had choroideal neovascularisation(CNV).Before the use of indocyanine green(ICG) angiography,occult CNV was detected in only 1.8% of the eyes,but after the use of ICG angiography,this increased to 19.5%(P<0.001).Of the 349 eyes which were followed up,visual acuity had remained stable in 68.2% of the eyes.There was a statistically significant relationship between localisation of lesion and visual acuity changes on pre-and post-laser treatment(P<0.001).Also there was a statistically significant relationship between localisation of lesion and recurrence(P<0.05).The recurrence was less in subfoveal lesions than that in juxtafoveal and extrafoveal lesions.· CONCLUSION:ICG angiography is highly important in the treatment of occult CNV.

Low-Spatial Coherence High-Power Electrically Injected 6xx nm Dual-Emitter Laser

Laser-based displays have attracted much attention owing to large-size screen and full-color gamut compared with other displays such as liquid crystal display and light emitting diode. However, there exists a phenomenon, speckle, limits the applications of laser display because of the high coherence of laser. In this work, we developed an electrically injected 6xx nm dual-emitter laser which combines the low-spatial coherence with the high-power. The output power of the dual-emitter laser exceeds 500 mW under 20?C pulse operation. The single emitter consists of D-shaped section used to obtain more independent spatial modes thus reduces coherence and a stripe area to obtain the high power. The radius of the D-shaped cavity is 500 μm and the length of stripe is 1000 μm. We used the standard photolithography and inductively coupled plasma (ICP) process to fabricate the device. The speckle contrast was measured to be 5%. It exhibits a great potential of reducing speckle from the source directly for laser display.

The Case Report on the Effectiveness of Infrared Light on Acid Burn Victim

Burn injuries are common in Pakistan. However, most people are reluctant to have infrared treatment for their wounds. This study investigated the efficacy of infrared treatment on burn wounds. The procedure involved a burn victim who had sustained acid burns to the neck and face. Nectrotomy was done to remove dead tissue from the burn wound, and after treatment, Low-Level Light was used to reduce pain and enhance healing in the patient. Initial results showed mild hypertrophic scars, no stiffness. Post-operation therapy included physical training regimens and massage. The patient showed satisfactory results and felt less tightness in neck movements by the following treatment. The article concludes by showing that infrared light promoted repair and regrowth at a cellular level.

亚长脉冲1064 nm Nd:YAG激光治疗面部毛细血管扩张的临床观察

目的 观察亚长脉冲1064 nm Nd:YAG激光治疗面部毛细血管扩张的临床疗效及安全性。方法 选取医院2022年5月-2022年12月收治的30例面部毛细血管扩张患者,全部患者均使用Fotona亚长脉冲1064 nm Nd:YAG激光治疗,调节为亚长脉冲ACC模式(250μs),手具为R28,能量密度为130-160J/cm2,光斑大小2mm,频率1.6Hz。观察患者治疗效果、主要症状缓解时间、疼痛程度、满意度、不良反应及复发情况结果 30例患者总有效率为96.67%;患者面部毛细血管扩张、红色斑块、皮肤瘙痒症状缓解时间分别为(2.45±0.61)d、(2.30±0.47)d、(3.11±0.74)d;患者治疗期间平均VAS评分为(2.12±0.25)分;患者总满意度为90.00%,不良反应发生率为6.67%;患者随访3个月内无复发。结论 面部毛细血管扩经亚长脉冲1064 nm Nd:YAG激光治疗,主要症状一般3-5天消退,治疗过程中疼痛程度轻微,耐受性好,不良反应少,复发率低,患者满意度高。

Watt-level acousto-optically Q-switched Pr:YLF laser at 639 nm

We present a study on a watt-level acousto-optically Q-switched Pr:YLF laser at three different repetition rates(10 kHz,20 kHz,and 50 kHz)for the first time,to the best of our knowledge.The corresponding average output powers and pulse widths were measured to be 1.14 W,1.2 W,and 1.32 W,and 40 ns,52 ns,and 80 ns,respectively.A maximum pulse energy of0.11 mJ was obtained,corresponding to a peak power of up to 2.8 kW at a repetition rate of 10 kHz.The simulated dynamics of a fast Q-switched Pr:YLF laser is in agreement with the experiment.The laser's ability to generate stable pulses with high peak power and short pulse width makes it highly desirable for various practical applications,such as laser machining and material processing.

点阵CO_(2)激光联合强脉冲光治疗痤疮后瘢痕疗效观察

目的:探讨点阵CO_(2)激光联合强脉冲光对痤疮后瘢痕患者的瘢痕面积、红肿面积及愈合时间的影响。方法:选取2020年1月-2020年12月于笔者医院就诊的90例痤疮后瘢痕患者为研究对象,按照随机数字表法分为两组。对照组(45例)行点阵CO_(2)激光治疗,研究组(46例)在对照组治疗基础上联合强脉冲光治疗。比较两组疗效、生活质量、痤疮瘢痕权重评分(Echelle d’evaluation clinique des cicatrices d’acne, ECCA)、瘢痕面积、红肿面积及愈合时间。结果:研究组总有效率93.48%,高于对照组73.33%,两组比较差异有统计学意义(P<0.05)。治疗后两组痤疮患者特异性生活质量问卷(Acne-specific quality of life questionnaire, Acne-QoL)各维度评分均高于治疗前,且研究组Acne-QoL各维度评分均高于对照组,差异有统计学意义(P<0.05)。治疗后两组ECCA评分均低于治疗前,且研究组ECCA评分低于对照组,差异均有统计学意义(P<0.05);治疗后两组瘢痕面积、红肿面积均小于治疗前(P<0.05),且研究组瘢痕面积、红肿面积小于对照组(P<0.05),研究组愈合时间短于对照组,差异均有统计学意义(P<0.05)。结论:点阵CO_(2)激光联合强脉冲光治疗痤疮后瘢痕有效率高,能改善患者生活质量与ECCA评分,缩小瘢痕面积及红肿面积,缩短愈合时间。

980 nm红激光经尿道膀胱肿瘤整块切除与经尿道膀胱肿瘤电切术治疗非肌层浸润性膀胱癌的疗效比较

目的比较980 nm红激光经尿道膀胱肿瘤整块切除与经尿道膀胱肿瘤电切术(transuretheral resection of bladder tumor,TUR-Bt)治疗非肌层浸润性膀胱癌(non-muscle invasive bladder cancer,NMIBC)的安全性和有效性。方法回顾性分析2017年4月~2019年9月我院144例NMIBC的临床资料,体内有金属植入物者行980 nm红激光经尿道膀胱肿瘤整块切除(980 nm红激光组,n=68),其余行TUR-Bt(TUR-Bt组,n=76),术后均接受规范性膀胱灌注治疗。比较2组手术时间、膀胱冲洗时间、保留导尿时间、术后住院时间和闭孔神经反射、膀胱穿孔等围手术期并发症发生情况。结果2组均顺利完成手术,其中980 nm红激光组无一例中转开放手术,TUR-Bt组2例中转开放手术。980 nm红激光组手术时间(21.6±3.8)min,与TUR-Bt组(22.3±3.2)min差异无统计学意义(t=1.200,P=0.195)。980 nm红激光组膀胱冲洗例数及时间、导尿管留置时间、住院时间均明显少于/短于TUR-Bt组(P<0.05)。TUR-Bt组分别有8、5例发生闭孔神经反射及膀胱穿孔,980 nm红激光组无一例发生闭孔神经反射及膀胱穿孔,2组差异有统计学意义(P=0.005,P=0.038)。术后病理证实均为非肌层浸润性尿路上皮癌。2组患者术后随访12个月,980 nm红激光组复发2例,TUR-Bt组复发4例,2组肿瘤复发率无统计学差异(χ^(2)=0.078,P=0.081)。结论980 nm红激光整块切除法治疗NMIBC安全、有效。与TUR-Bt相比,980 nm红激光围手术期并发症少,可获得精确病理分期,肿瘤复发率相似。

LD泵浦1.2W连续Nd:YAG/LBO红光激光器

报道了一种光纤耦合LD泵浦Nd∶YAG晶体、腔内Ⅰ类临界相位匹配LBO倍频、瓦级连续输出的全固态红光激光器的设计和实验结果。采用短三镜折叠腔结构,在8W的注入泵浦功率下,获得了连续输出1.2W、波长为660nm的红光基模输出,光光转化效率达到15%。

准连续660nm Nd:YAG内腔倍频激光器的研究

研制了一台Nd :YAG内腔倍频输出 6 6 0nm红光激光器。分析了腔长对激光功率的影响 ,采用新型径向调整式光学镜片调整架 ,平—平腔结构 ,腔长 390mm ,双灯泵浦 ,KTP晶体内腔倍频 ,并设置声光Q开关 ,获得 6 6 0nm红光输出 2W。

LD泵浦Nd∶YVO_4晶体LBO临界相位匹配倍频671nm激光器

报道了国产LD泵浦Nd∶YVO4 晶体 ,首次用临界相位匹配方式LBO腔内倍频实现了高效率的 6 71nm红激光输出。当注入泵浦功率为 80 0mW时 ,用II类临界相位匹配LBO倍频 ,红激光基模输出 5 2mW ,光 光转换效率达 6 .5 %;用I类临界相位匹配LBO倍频 ,红激光基模输出 97mW ,光 光转换效率达 12 .1%。

基于线结构激光传感器的土壤表面粗糙度测量方法研究

土壤表面粗糙度是农作物种植、灌溉和收获等田间管理必须考虑的作业参数,也是精准农业发展中亟待解决的关键问题之一。针对土壤表面粗糙度缺乏快速检测手段的问题,提出一种基于线结构激光传感器的土壤表面粗糙度测量方法。利用半导体红光激光器、CCD工业相机、计算机及支架等构建测量系统,采集土壤样本的表面图像数据,借助MATLAB获取其三维点云模型,实现土壤表面的三维曲面建模并计算曲面面积。定义土壤表面三维曲面面积与其平面面积的比值为表征土壤表面粗糙度的量,并通过对比4个颗粒度土壤样本的该值范围,确定了判别样本表面粗糙度的阈值。利用3种土槽旋耕土壤表面样本对系统和算法进行验证,比值处于1.214～1.939之间,检测结果均与样本实际特征相符合。该方法能够检测和判断土壤表面的颗粒粗糙程度。